Columbium base alloy



United States Patent ice 3,113,853 COLUMBIUM BASE ALLOY Winston H. Chang, Cincinnati, and Jack W. Clark, Milford, Ulric, assignors to General Electric Company, a corporation of New York No Drawing. Filed May 31, 1960, Ser. No. 32,581 3 Claims. (Cl. 75-174) This invention relates to columbium base alloys and, more particularly, to columbium base alloys hardened by both solution hardening through tungsten and molybdenum and dispersion hardening through a combination of zirconium, hafnium and titanium in the presence of carbon.

The development of columbium base alloys includes improvement in both strength as well as in oxidation resistance. Generally, however, an alloy which finally finds its way into production is neither the strongest alloy available nor the one having the best oxidation resistance. It is an alloy having the best combination of strength and oxidation resistance along with suitable ductility to allow it to be fabricated.

Various columbium base alloys achieve their strength through two co-acting mechanisms. One of these mechanisms is solution hardening in which certain judiciously selected quantities of particular substitutional elements are put into a single phase or solid solution with the base metal. This is generally accomplished during vacuum arc melting of the alloy. Another of the co-acting strengthening mechanisms is dispersion hardening in which other judiciously selected quantities of particular substitutional elements are included in the alloy along with such interstitial elements as. carbon or oxygen or both to form fine, well dispersed and thermodynamically stable particles of carbides or oxides or both. The presence of such a fine, well dispersed phase within the matrix of a metal alloy is very effective in inhibiting motion of dislocations and thereby slip during long time constant load stress rupture conditions.

The principal object of this invention is to provide an improved columbium base alloy having a good balance of strength and oxidation resistance and having a strong matrix reinforced by a fine dispersion of complex highly stabilized carbides.

Another object is to provide an improved columbium base alloy which is both solution and dispersion hardened to give improved strength properties through carbides of titanium, zirconium and hafnium and a judicious ratio of carbide former to carbon.

These and other objects and advantages will become more readily apparent from the following more detailed description which is meant to be exemplary and not a limitation on the broad scope of the invention.

Briefly, this invention provides a columbium base alloy solution hardened with tungsten and molybdenum and dispersion hardened with 0.1-1% by weight titanium, 0.11.8% by weight zirconium and 0.5-1% by weight hafnium in the presence of carbon to form dispersed simple and complex carbides of titanium, zirconium and hafnium.

The columbium base alloy described in co-pending application Serial Number 819,776, Frank, filed June 11, 1959, now US. Patent 2,973,261, issued February 28, 1961, and assigned to the assignee of the present invention, is an example of a columbium base alloy solution hardened with a judicious selection of one or both of the elements tungsten and molybdenum within the range of 420% by weight. In addition, that alloy is dispersion hardened with about 0=.1-1.8%- by Weight zirconium and optionally up to 1% by weight titanium in the presence of 3,113,853 Patented Dec. 10, 1963 a up to about 0.3% by weight carbon and optionally up to about 0.25% by weight oxygen.

It has been found through the present invention that a dramatic increase in strength without loss of oxidation resistance can be achieved in such an alloy, particularly with the larger amounts of tungsten and molybdenum, through the judicious use of 0.5-1% by Weight hafnium along with titanium and zirconium in the presence of carbon to form highly stabilized complex carbides well dispersed throughout the solution hardened Cb-Mo-W matrix.

A preferred form of the present invention is an alloy consisting essentially of, in percent by weight, 1520% W, 540% Mo, 0.5-1% Zr, 0.050.1% C, (LS-1% Hf, O.10.25% Ti with the balance columbium. In another form, small amounts of boron can be added in order to further improve strength properties.

The following Table I provides the composition of some typical alloys Within and Without the scope of this invention which were melted and tested. These alloys were vacuum arc melted in five pound heats, extruded and swaged to diameter stock.

TABLE I Percent By Weight Alloy W Mo Zr 0 Hi Ti B G b 20 10 1 Balance. 20 10 0. 5 Do. 15 5 0. 5 D0. 15 5 0. 5 DO. 15 5 1 Do.

Tables II and III below report the results of tensile and stress rupture tests conducted in vacuum on the swaged alloys.

TABLE II Tensile Properties Ultimate Strength 0.2% Yield Strength (1,000 p.s.1.) (1,000 p.S.i.) Alloy 2,000 F. 2,200 F. 2,000 F. i 2,200 F.

AS 11 61.2 58. 0 AS 10 90. 0 64. 2 86. 4 55. 5 AS 7 59. 8 50. 3 51. 3 48. 3 AS 12 52. 0 45. 2 48.4 40.0 F 8-1 64 48 50 35 TABLE III Stress Rupture Properties Life (hrs. Alloy 35,000 p.s.i.

. and 2,000 F.)

AS 10 104.12 AS 7 u 48. 07 AS 12. 19. 7 F 8-1 20 Although the preferred form of the alloy of this invention is represented by the range of alloys AS 10 and 11 (which are significantly stronger in all respects) and specifically the composition of AS 10, it can be recognized that alloy AS 7, within the range of this invention results in improved tensile strength properties at 2200" F. and improved 0.2% yield stnength and stress rupture life at 2000 F. in comparison with the strongest alloy of the abovementioned co-pending application, herein represented as alloy F 8-1. The dramatic increase in the 3 tensile properties of alloys AS 10 and 11 is readily seen in Table II.

As represented in Table III, the stress rupture strength of the alloy of this invention, and particularly AS 10, is dramatically greater than similar alloys which are not as judiciously solution and dispersion hardened through the careful selection of the elements Within the scope of the present invention. Another Way of representing the greatly improved stress rupture properties of the specifically preferred alloy form AS 10 in comparison with alloy F 8-1 is to note that the 2200 F1100 hour stress rupture life of AS 10 is 22,000 psi. in comparison with 16,500 p.s.i. for alloy form F 8-1.

Although the present invention has been described in connection with specific examples, it will be understood by those skilled in the art, that the modifications and variations of which this invention is capable fall within the broad concept of a judicious selection of the element hafnium along With titanium and zirconium, in the presence of carbon to provide improved dispersion hard ening to a solution hardened columbium base alloy.

What is claimed is:

1. An improved columbium base ailloy consisting esi sentially, in percent by weight, of 15-20% W, 510% M0, 0.51% Zr, ODS-0.1% C, O.51% Hf, (ll-0.25% "Di, up to about 0.05% B With the balance oolumbium.

2. An improved columbium base alloy consisting essentially, in percent by weight, of 20% W, 10% M0,

0.5% Zr, 0.1% C, 1% Hf, 0.25% Ti, with the balance columbium.

3. An improved columbium base alloy consisting essentially, in percent by Weight, of 20% W, 10% Mo, 1% Zr, 0.1% C, 0.5% Hf, 0.1% Ti, 0.05% B, with the balance oolumbium.

References Cited in the file of this patent UNITED STATES PATENTS 

1. AN IMPROVED COLUMBIUM BASE ALLOY CONSISTING ESSENTIALLY, IN PERCENT BY WEIGHT, OF 15-20% W, 5-10% MO, 0.5-1% ZR, 0.05-0.1% C, 0.5-1% HF, 0.1-0.25% TI, UP TO ABOUT 0.05% B WITH THE BALANCE COLUMBIUM. 